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package java.awt.dnd;

import java.awt.event.InputEvent;

/**
 * The <code>DragSourceDragEvent</code> is
 * delivered from the <code>DragSourceContextPeer</code>,
 * via the <code>DragSourceContext</code>, to the <code>DragSourceListener</code>
 * registered with that <code>DragSourceContext</code> and with its associated
 * <code>DragSource</code>.
 * <p>
 * The <code>DragSourceDragEvent</code> reports the <i>target drop action</i>
 * and the <i>user drop action</i> that reflect the current state of
 * the drag operation.
 * <p>
 * <i>Target drop action</i> is one of <code>DnDConstants</code> that represents
 * the drop action selected by the current drop target if this drop action is
 * supported by the drag source or <code>DnDConstants.ACTION_NONE</code> if this
 * drop action is not supported by the drag source.
 * <p>
 * <i>User drop action</i> depends on the drop actions supported by the drag
 * source and the drop action selected by the user. The user can select a drop
 * action by pressing modifier keys during the drag operation:
 * <pre>
 *   Ctrl + Shift -&gt; ACTION_LINK
 *   Ctrl         -&gt; ACTION_COPY
 *   Shift        -&gt; ACTION_MOVE
 * </pre>
 * If the user selects a drop action, the <i>user drop action</i> is one of
 * <code>DnDConstants</code> that represents the selected drop action if this
 * drop action is supported by the drag source or
 * <code>DnDConstants.ACTION_NONE</code> if this drop action is not supported
 * by the drag source.
 * <p>
 * If the user doesn't select a drop action, the set of
 * <code>DnDConstants</code> that represents the set of drop actions supported
 * by the drag source is searched for <code>DnDConstants.ACTION_MOVE</code>,
 * then for <code>DnDConstants.ACTION_COPY</code>, then for
 * <code>DnDConstants.ACTION_LINK</code> and the <i>user drop action</i> is the
 * first constant found. If no constant is found the <i>user drop action</i>
 * is <code>DnDConstants.ACTION_NONE</code>.
 *
 * @since 1.2
 */

public class DragSourceDragEvent extends DragSourceEvent {

  private static final long serialVersionUID = 481346297933902471L;

  /**
   * Constructs a <code>DragSourceDragEvent</code>.
   * This class is typically
   * instantiated by the <code>DragSourceContextPeer</code>
   * rather than directly
   * by client code.
   * The coordinates for this <code>DragSourceDragEvent</code>
   * are not specified, so <code>getLocation</code> will return
   * <code>null</code> for this event.
   * <p>
   * The arguments <code>dropAction</code> and <code>action</code> should
   * be one of <code>DnDConstants</code> that represents a single action.
   * The argument <code>modifiers</code> should be either a bitwise mask
   * of old <code>java.awt.event.InputEvent.*_MASK</code> constants or a
   * bitwise mask of extended <code>java.awt.event.InputEvent.*_DOWN_MASK</code>
   * constants.
   * This constructor does not throw any exception for invalid <code>dropAction</code>,
   * <code>action</code> and <code>modifiers</code>.
   *
   * @param dsc the <code>DragSourceContext</code> that is to manage notifications for this event.
   * @param dropAction the user drop action.
   * @param action the target drop action.
   * @param modifiers the modifier keys down during event (shift, ctrl, alt, meta) Either extended
   * _DOWN_MASK or old _MASK modifiers should be used, but both models should not be mixed in one
   * event. Use of the extended modifiers is preferred.
   * @throws IllegalArgumentException if <code>dsc</code> is <code>null</code>.
   * @see java.awt.event.InputEvent
   * @see DragSourceEvent#getLocation
   */

  public DragSourceDragEvent(DragSourceContext dsc, int dropAction,
      int action, int modifiers) {
    super(dsc);

    targetActions = action;
    gestureModifiers = modifiers;
    this.dropAction = dropAction;
    if ((modifiers & ~(JDK_1_3_MODIFIERS | JDK_1_4_MODIFIERS)) != 0) {
      invalidModifiers = true;
    } else if ((getGestureModifiers() != 0) && (getGestureModifiersEx() == 0)) {
      setNewModifiers();
    } else if ((getGestureModifiers() == 0) && (getGestureModifiersEx() != 0)) {
      setOldModifiers();
    } else {
      invalidModifiers = true;
    }
  }

  /**
   * Constructs a <code>DragSourceDragEvent</code> given the specified
   * <code>DragSourceContext</code>, user drop action, target drop action,
   * modifiers and coordinates.
   * <p>
   * The arguments <code>dropAction</code> and <code>action</code> should
   * be one of <code>DnDConstants</code> that represents a single action.
   * The argument <code>modifiers</code> should be either a bitwise mask
   * of old <code>java.awt.event.InputEvent.*_MASK</code> constants or a
   * bitwise mask of extended <code>java.awt.event.InputEvent.*_DOWN_MASK</code>
   * constants.
   * This constructor does not throw any exception for invalid <code>dropAction</code>,
   * <code>action</code> and <code>modifiers</code>.
   *
   * @param dsc the <code>DragSourceContext</code> associated with this event.
   * @param dropAction the user drop action.
   * @param action the target drop action.
   * @param modifiers the modifier keys down during event (shift, ctrl, alt, meta) Either extended
   * _DOWN_MASK or old _MASK modifiers should be used, but both models should not be mixed in one
   * event. Use of the extended modifiers is preferred.
   * @param x the horizontal coordinate for the cursor location
   * @param y the vertical coordinate for the cursor location
   * @throws IllegalArgumentException if <code>dsc</code> is <code>null</code>.
   * @see java.awt.event.InputEvent
   * @since 1.4
   */
  public DragSourceDragEvent(DragSourceContext dsc, int dropAction,
      int action, int modifiers, int x, int y) {
    super(dsc, x, y);

    targetActions = action;
    gestureModifiers = modifiers;
    this.dropAction = dropAction;
    if ((modifiers & ~(JDK_1_3_MODIFIERS | JDK_1_4_MODIFIERS)) != 0) {
      invalidModifiers = true;
    } else if ((getGestureModifiers() != 0) && (getGestureModifiersEx() == 0)) {
      setNewModifiers();
    } else if ((getGestureModifiers() == 0) && (getGestureModifiersEx() != 0)) {
      setOldModifiers();
    } else {
      invalidModifiers = true;
    }
  }

  /**
   * This method returns the target drop action.
   *
   * @return the target drop action.
   */
  public int getTargetActions() {
    return targetActions;
  }


  private static final int JDK_1_3_MODIFIERS = InputEvent.SHIFT_DOWN_MASK - 1;
  private static final int JDK_1_4_MODIFIERS =
      ((InputEvent.ALT_GRAPH_DOWN_MASK << 1) - 1) & ~JDK_1_3_MODIFIERS;

  /**
   * This method returns an <code>int</code> representing
   * the current state of the input device modifiers
   * associated with the user's gesture. Typically these
   * would be mouse buttons or keyboard modifiers.
   * <P>
   * If the <code>modifiers</code> passed to the constructor
   * are invalid, this method returns them unchanged.
   *
   * @return the current state of the input device modifiers
   */

  public int getGestureModifiers() {
    return invalidModifiers ? gestureModifiers : gestureModifiers & JDK_1_3_MODIFIERS;
  }

  /**
   * This method returns an <code>int</code> representing
   * the current state of the input device extended modifiers
   * associated with the user's gesture.
   * See {@link InputEvent#getModifiersEx}
   * <P>
   * If the <code>modifiers</code> passed to the constructor
   * are invalid, this method returns them unchanged.
   *
   * @return the current state of the input device extended modifiers
   * @since 1.4
   */

  public int getGestureModifiersEx() {
    return invalidModifiers ? gestureModifiers : gestureModifiers & JDK_1_4_MODIFIERS;
  }

  /**
   * This method returns the user drop action.
   *
   * @return the user drop action.
   */
  public int getUserAction() {
    return dropAction;
  }

  /**
   * This method returns the logical intersection of
   * the target drop action and the set of drop actions supported by
   * the drag source.
   *
   * @return the logical intersection of the target drop action and the set of drop actions
   * supported by the drag source.
   */
  public int getDropAction() {
    return targetActions & getDragSourceContext().getSourceActions();
  }

    /*
     * fields
     */

  /**
   * The target drop action.
   *
   * @serial
   */
  private int targetActions = DnDConstants.ACTION_NONE;

  /**
   * The user drop action.
   *
   * @serial
   */
  private int dropAction = DnDConstants.ACTION_NONE;

  /**
   * The state of the input device modifiers associated with the user
   * gesture.
   *
   * @serial
   */
  private int gestureModifiers = 0;

  /**
   * Indicates whether the <code>gestureModifiers</code> are invalid.
   *
   * @serial
   */
  private boolean invalidModifiers;

  /**
   * Sets new modifiers by the old ones.
   * The mouse modifiers have higher priority than overlaying key
   * modifiers.
   */
  private void setNewModifiers() {
    if ((gestureModifiers & InputEvent.BUTTON1_MASK) != 0) {
      gestureModifiers |= InputEvent.BUTTON1_DOWN_MASK;
    }
    if ((gestureModifiers & InputEvent.BUTTON2_MASK) != 0) {
      gestureModifiers |= InputEvent.BUTTON2_DOWN_MASK;
    }
    if ((gestureModifiers & InputEvent.BUTTON3_MASK) != 0) {
      gestureModifiers |= InputEvent.BUTTON3_DOWN_MASK;
    }
    if ((gestureModifiers & InputEvent.SHIFT_MASK) != 0) {
      gestureModifiers |= InputEvent.SHIFT_DOWN_MASK;
    }
    if ((gestureModifiers & InputEvent.CTRL_MASK) != 0) {
      gestureModifiers |= InputEvent.CTRL_DOWN_MASK;
    }
    if ((gestureModifiers & InputEvent.ALT_GRAPH_MASK) != 0) {
      gestureModifiers |= InputEvent.ALT_GRAPH_DOWN_MASK;
    }
  }

  /**
   * Sets old modifiers by the new ones.
   */
  private void setOldModifiers() {
    if ((gestureModifiers & InputEvent.BUTTON1_DOWN_MASK) != 0) {
      gestureModifiers |= InputEvent.BUTTON1_MASK;
    }
    if ((gestureModifiers & InputEvent.BUTTON2_DOWN_MASK) != 0) {
      gestureModifiers |= InputEvent.BUTTON2_MASK;
    }
    if ((gestureModifiers & InputEvent.BUTTON3_DOWN_MASK) != 0) {
      gestureModifiers |= InputEvent.BUTTON3_MASK;
    }
    if ((gestureModifiers & InputEvent.SHIFT_DOWN_MASK) != 0) {
      gestureModifiers |= InputEvent.SHIFT_MASK;
    }
    if ((gestureModifiers & InputEvent.CTRL_DOWN_MASK) != 0) {
      gestureModifiers |= InputEvent.CTRL_MASK;
    }
    if ((gestureModifiers & InputEvent.ALT_GRAPH_DOWN_MASK) != 0) {
      gestureModifiers |= InputEvent.ALT_GRAPH_MASK;
    }
  }
}
